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Discussion Starter #1 (Edited)
I'm rebuilding a B20B engine basically from scratch and I'm looking to get some more HP out of it. What should I do to the block and what other equipment should I lob in there to ensure good 140ish horsepower without compromising low-end torque and reliability? I've just landed a new job so I've got the resources but not quite the time for it so it's going to be a slow project :D

If possible, I'd like to retain the twin SU's I have now as they are in good working order
 

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The most important thing is improving flow through the head. You should have that work done by an experienced professional, although it doesn't have to be a Volvo specialist. It's easy to do more harm than good if you try it yourself.

Do not fit larger valves -- that works against you.

Shave the head so the chamber volume is 52cc and use the .8mm head gasket.

Bore the block to 90mm, which is a large as makes sense with the B head.

Deck the block so the new pistons come up even with the deck at TDC. They probably won't all be even, but you can remove metal from the crowns of the taller pistons so they all match the shortest piston/rod stack. It's best to do a test assembly before the final decking.

A Volvo D cam will improve power with no noticeable loss of low-end torque. This will be compatible with your SUs, which should have KD needles fitted.

Lightening the flywheel won't add any HP, but it will improve acceleration in the lower gears. Simply remove as much as possible from the clutch side outboard of the pressure plate without going quite all the way down to the ring gear. It only takes of 1.5 kilos or so, but it will make a difference.

Have everything balanced. It won't add power, but it makes the engine much more pleasant.
 

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Discussion Starter #3
Thank you for your answer!

Is the overbore important? It's at it's stock bore and if I don't completely overbore it I can bore it when I've done a million miles on it and the cylinders are all scratched up :D
 

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The overbore is not all that important for performance, but I assumed you were planning on new pistons, which would require some amount of boring. 90mm is not particularly large as far as the block goes, it's the bore that's the best match for the combustion chambers in the B head.
 

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Discussion Starter #5
I got a good price for the new pistons and overbore so I'm having it done soon! For the head I'm still to find someone who knows what they're doing
 

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Discussion Starter #6
I pulled apart a B18 while waiting to acquire all parts for the B20 rebuild and I came across an aftermarket camshaft with the following markings on it, front to back

(1) (1) [inside spheres] (J) (5) K-235-C MADE IN UK LYD 5 S-733

any idea where I could find more information about it? or should I just try to measure the lift and duration? It's in good shape
 

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Discussion Starter #11
It seems that the head will be ready weeks later than other engine parts. Will it be OK to run the new inside parts in with a slightly planed B20A head before the custom head is finished?
 

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Discussion Starter #12
It seems that the head will be ready weeks later than other engine parts. Will it be OK to run the new inside parts in with a slightly planed B20A head before the custom head is finished?
And to continue on that, what is a sufficient run in for all new insides for maximum reliability? I was thinking of running one day on idle, changing oils and then running 500 miles very carefully and changing oils again, adjusting valve clearances when necessary

For oil I was planning 10W30 mineral, unless the valvoline racing 20W50 is on sale, I've heard it has useful additives
 

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You must use a break-in additive meant for use with flat tappet cams. A good parts store will have it.

You want the engine to start with as little cranking as possible. Take the covers off the SU float bowls and fill them halfway with gas (then put the covers back on, of course). Fill the oil filter halfway and then spin it on quickly. Make sure the ignition timing is close to right. The battery should be fully charged. Don't forget to hook up the engine ground strap.

Start the engine and run it at 2000 RPM for at least 20 minutes. You can rev it higher than that briefly, but do NOT let it idle. Then turn it off, drain the oil and toss out the filter. Let it all cool down fully.

Replace the oil and filter (if you have some break-in additive left, put that in, but it's not strictly necessary). Remove the rocker assembly and retorque the head. Put the rockers back on and readjust the valves. Start the engine and warm it up at a fast idle, then you can let it idle long enough to tune the SUs and check the timing. As soon as possible, drive the car -- you don't need to go find the redline just yet, but use plenty of throttle. You need pressure in the cylinders to seat the rings. If you don't do this early, they may never seat fully.

Work progressively up to higher revs over the first 150 km or so. After that, you can drive it however you want.

When you put the modified head on, you don't need to break anything in over again. You do need to do the retorque and readjust the valves.
 

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Discussion Starter #14
Oh interesting! Glad I asked! :) Thank you very much!

I got the break-in additive free with the cam, and both the cam and the lifter packaging are most insistent on using it :D

10 degrees before TDC should be close enough shouldn't it?
 

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Discussion Starter #16
Cheers :)

I think I'm going with Gulf SAE 30 Classic oil for the break-in, it should have plenty of ZDDP and other poisons to minimize the risks involved
 

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Discussion Starter #17
I had to have the cylinders overbored anyway, #3 was going elliptic so I ordered a new set of 0.030 over Mahle pistons :) hoping for delivery next week so I can get this going again
 

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Discussion Starter #18
I should have the engine close to running soon, I have thursday and friday off this week :)

Any idea which of the 123ignition advance curves would be best suited for the modifications?
 

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Discussion Starter #19
Took quite a bit of cranking because the old pointy diz' didn't give a spark so I had to change to the new one :facepalm: but eventually it fired up and ran beautifully. I even drove about half a mile but I have to adjust the clutch to be able to go further
 

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Great progress on this! I'm sure you haven't thrashed it yet, but how does it feel overall?

My daughter and I are starting assembly of my over-bored B18 this weekend ourselves after getting the a B20 head rebuilt, crank balanced, and flywheel turned. Just have to order a few remaining bits from VPAutoparts and get her shoved into the 444.
 
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